FHM stands for "For Him Magazine" - an English mens' magazine. That's "mens'" as in fast cars, fast computers, and excessive drunkenness, not as in cover-to-cover spreadeagled naked women.
Well, there may be a few in there, but topless shots only.
FHM is widely regarded as softcore porn for those too gutless to buy a porn mag, but only by people who don't actually read it.